8o 



SCIENCE OF SUCCESSFUL THRESHING 



The friction wheel on this has inner and outer flanges on 

 the rim. The friction band consists of a flexible strap of 

 steel with wooden blocks attached to it to form the friction 

 surfaces. The desired tension on the band is obtained 

 by means of the adjusting screw with hand-wheel. The 

 brake-arm rests on a knife-edge on the top of a post which 

 in turn rests on a platform scale. Overheating is prevented 



FIG. 23. PRONY BRAKE. 



by keeping a flow of cooling water on the inside of the rim. 

 Centrifugal force and the flanges hold the water against 

 the inside of the rim when the wheel is in motion. A 

 pipe with its end in the form of a scoop removes the heated 

 water while another continually discharges fresh water 

 into the rim. Heavy grease is applied to the rubbing 

 surfaces. 



